Typically, a semiconductor device includes a plurality of layers on a silicon substrate, which are deposited on the silicon substrate through a deposition process. Such deposition process has several important issues, which are important in evaluating the deposited layers and selecting the deposition process.
First, an example of the issues is ‘quality’ of the deposited layer. The ‘quality’ represents composition, contamination levels, defect density, and mechanical and electrical properties. The composition of each of the layers may be changed according to conditions of the deposition process. This is very important for obtaining a specific composition.
Second, another example of the issues is a uniform thickness over the wafer. Specifically, a thickness of a film deposited on a pattern having a non-planar shape with a stepped portion is very important. Here, whether the thickness of the deposited film is uniform may be determined through a step coverage which is defined as a ratio of a minimum thickness of the film deposited on the stepped portion divided by a thickness of the film deposited on the pattern.
Another issue respect to the deposition is a filling space. This represents a gap filling in which an insulating layer including an oxide layer is filled between metal lines. A gap is provided to physically and electrically isolate the metal lines from each other.
Among the issues, uniformity is one of very important issues with respect to the deposition process. A non-uniform layer may cause high electrical resistance on the metal lines to increase possibility of mechanical damage.